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How much of a concern is this? I've heard that even with the solvents in top tier gasolines that carbon deposits can still form under high load, low RPM conditions. Any thoughts on this?

Hi Jhu:

___Been driving for FE for far to long and if their were any reason to worry, I would be living proof. I have not been in the Accord's top end but have swiped the tail pipe and its cleaner than any other vehicle that I have done the same in. Tail pipe deposits are not necessarily an indication of carbon deposits on the valves but detergent gasoline’s have removed this problem years ago.

___Good Luck

___Wayne

I think injected vehicles are probably largely immune to this. Carb'd car drivers need to do what diesel drivers do, kick them in the ass once in a while to blow the undesirables out.

It probably isn't the worst idea in the world to occasionally use one of the FI cleaning additives in your tank-Chevron Techron or any of the others.One that redissolves the water isn't a bad idea since you almost always get a tiny bit of water(from humid air getting in, filling above the fuel,and condensing out at night when it cools).

I doubt you actually need it, but I use them once or twice a year.

I usually stick with a name brand gas-shell 87 octane- but I have a suspicion that the cheapo offbrands might actually be exactly the same-maybe not-but...I kinda doubt the refineries bother to change-cheap down- the additive package for the the brand X gas they produce.Maybe they actually change the additive pk, but that would mean producing it in a different rus, or at least adding it at the end in 2 steps/ 2 batches."Uh, I have to add 5 gallons of additive to 100,000 gallons of shell, but just 3 gallons to brand X."
If the additive isn't terribly expensive, it would be easier to do it just once.

Does anyone out there actually know how refineries do the additive pk for "offbrand" gas
Charlie
PS-I doubt P&G causes buildup with modern gas-especially if you hold off on motor off P&G until the engine is up to temp.

Have there been any reports of the Prius developing deposits? It P&Gs more than any pure ice P&Ger will.

I haven't heard of any problems, so I suspect P&G doesn't cause a problem.
Charlie

Additives are generally added in the tanker truck at the pipeline terminal.

Around my hometown, I see station tanks being filled by trucks from the same regional distributors, pretty much regardless of the name on the stations' signs. I have no idea whether they put in different amounts of additives or different additives depending on the order. I regard gasolines of the same octane level as interchangeable. I haven't bought into the "top tier" hype.

Yaris
Thanks for the info. I have my doubts about the name brands also.
Charlie

If Wayne or anyone else in the Chicago/milwaukee area that P&Gs allot wants to help settle this question - pm me. I have a Snap-On digital video borescope. We can pull a spark plug(s) from the engine and I can get a clear image of the complete combustion chamber - top of piston, face of valves and depending on rotation the back of valves. It has a video out so if you have something that could record video from an RCA type input we could record it and post it here on the thread.

I'd be interested to see the outcome of this. I recently took apart the engine on my old civic. I wanted to see it's condition after putting up 100,000km on it. The engine had a total of 298,000km on it so it was interesting to see how little it was worn. I posted pictures over on ecomodder of it:http://ecomodder.com/forum/showthread.php/honda-civic-engine-parts-after-290-000km-9887.html
I never really p&g'ed it but did drive it gently for most of my time owning it. The exhaust valves were pitted and showed signs of leakage. The valves on one cylinder showed signs of being slightly toasted so may have been run too hot with my HAI?? Something you HAI fans should be mindful of.

I'm guessing that if a car is p&g'ed with the engine on then the carbon built up while idling would be burnt off during the pulse. If it's off during the glide then there's little or no carbon build up and what is, is burnt off during the pulse. The only other issue i can think of is bearing wear. Specifically big end bearing wear and camshaft bearing wear. Given the rather large amount of time the engine will spend actually starting (and therefore have less than ideal oil pressure) i'd be concerned about it's effects on those bearings.
Having said that, if it was causing harm, it would have shown up by now.

ollie

I'm guessing that if a car is p&g'ed with the engine on then the carbon built up while idling would be burnt off during the pulse. If it's off during the glide then there's little or no carbon build up and what is, is burnt off during the pulse.

Ah, yes good point about the pulse burning off the carbon deposits, if any. I hadn't considered that part.

Have there been any reports of the Prius developing deposits? It P&Gs more than any pure ice P&Ger will.

Don't be so sure. ;)